Backrest and method for making backrest

ABSTRACT

A backrest includes a frame, a web and a ring. The frame includes a margin and two rims extending on a side of the margin and a gap defined between the rims. The web is spread on the side of the frame. The ring is put on the web and fit in the annular groove so that the web is tightly spread on the frame.

FIELD OF INVENTION

The present invention relates to a backrest and, more particularly, to amethod for making such a backrest.

BACKGROUND OF INVENTION

A typical chair for use in an office includes a seat and a backrest. Theseat and the backrest are both made from foam material so as to providea soft feeling to a person sitting in the chair. However, the backrestmade of foam material is not good for dissipating heat produced by theperson. Moreover, the backrest made of foam material is heavy and bulkyand, hence, not economic regarding transportation.

The present invention is therefore intended to obviate or at leastalleviate the problems encountered in prior art.

SUMMARY OF INVENTION

It is an objective of the present invention to provide a backrest withgood dissipation of heat produced by a person's back laid against it.

It is another objective of the present invention to provide a backrestthat is light in weight and compact in size.

According to the present invention, a backrest includes a frame, a weband a ring. The frame includes a margin and two rims extending on a sideof the margin and a gap defined between the rims. The web is spread onthe side of the frame. The ring is put on the web and fit in the annulargroove so that the web is tightly spread on the frame.

Other objects, advantages and novel features of the invention willbecome more apparent from the following detailed description inconjunction with the attached drawings.

BRIEF DESCRIPTION OF DRAWINGS

The present invention will be described via detailed illustration ofembodiments referring to the drawings.

FIG. 1 is a flowchart of a method for making a backrest according to thepreferred embodiment of the present invention.

FIG. 2 is an exploded view of a backrest according to the preferredembodiment of the present invention.

FIG. 3 is a cross-sectional view of the backrest of FIG. 2.

FIGS. 4-9 are perspective views of a mold assembly in various steps ofthe method of FIG. 1 for making the backrest of FIG. 2.

FIG. 10 is a perspective view of the backrest of FIG. 1.

FIG. 11 is a perspective view of the backrest of FIG. 10 used in achair.

DETAILED DESCRIPTION OF EMBODIMENTS

In accordance with the preferred embodiment of the present invention, abackrest shown in FIGS. 2, 3, 10 and 11 is made in a method shown inFIGS. 1 and 4-9.

Referring to FIG. 2, the backrest includes a frame 10, a web 20, a ring30, a cushion 40 and a cover 50. The frame 10 includes a margin 11 andtwo rims 12 extending on a front side of the margin 11. A gap 13 isdefined between the rims 12.

Referring to FIG. 3, the web 20 is put on a front side of the frame 10.The ring 30 is put on a front side of the web 20. The ring 30 and anannular portion of the web 20 are fit into the annular groove 13. Thus,the web 20 is tightly spread on the frame 10, i.e., tension is producedin the web 20. The cushion 40 is put in the frame 10. The cushion 40 iscompressed between the margin 11 and the web 20. Thus, the web 20 ismore tightly spread on the frame 10, i.e., the tension in the web 20 isincreased. The cover 50 is installed around the frame 10.

Referring to FIGS. 1 and 4, at step S10, a mold assembly is provided.The mold assembly includes a lower mold 60, a middle mold 62 and anupper mold 70. The lower mold 60 defines a cavity 61 in an upper side.The profile of the cavity 61 is compliant with that of the backrest. Theprofile of the middle mold 62 is compliant with that of the cavity 61.

The upper mold 70 defines a cavity 71 in a lower side. The profile ofthe cavity 71 is compliant with that of the middle mold 62.

Referring to FIGS. 1 and 5, at step S15, the frame 10 is put in thecavity 61. The rims 12 face up.

Referring to FIGS. 1 and 6, at step S20, the middle mold 62 is loweredagainst the margin 11. Thus, the frame 10 is held in position. The rims12 are exposed.

Referring to FIGS. 1 and 7, at step S25, the web 20 is laid on themiddle mold 62. The web 20 covers the rims 12.

Referring to FIGS. 1 and 8, at step S30, the ring 30 is put on the web20. The ring 30 and an annular portion of the web 20 are forced into theannular groove 13. Thus, the web 20 is tightly spread on the frame 10.

Referring to FIGS. 1 and 9, at step S35, the upper mold 70 is loweredagainst the ring 30. High frequency is exerted on the frame 10, the web20 and the ring 30. Thus, the frame 10, the web 20 and the ring 30 areheated and therefore partly melted. The frame 10, the web 20 and thering 30 adhere to one another when they cool down.

Referring to FIG. 1, at step S40, the upper mold 70 is lifted from thering 30 and returned to its original position. The middle mold 62 islifted from the lower mold 60 and returned to its original position.

At step S45, the frame 10, the web 20 and the ring 30, as a whole, aremoved from the middle mold 62.

At step S50, the cushion 40 is put in the frame 10. The cushion 40 iscompressed between the margin 11 and the web 20. Thus, the web 20 ismore tightly spread on the frame 10.

At step S55, the cover 50 is installed around the frame 10.

At step S60, the backrest is finished.

The present invention has been described via detailed illustration ofsome embodiments. Those skilled in the art can derive variations fromthe embodiments without departing from the scope of the presentinvention. Therefore, the embodiments shall not limit the scope of thepresent invention defined in the claims.

1. A backrest including: a frame including a margin and two rimsextending on a side of the margin and a gap defined between the rims; aweb spread on the side of the frame; and a ring put on the web and fitin the annular groove so that the web is tightly spread on the frame. 2.The backrest according to claim 1 including a cushion arranged betweenthe margin and the web so that the web is more tightly spread on theframe.
 3. The backrest according to claim 1 including a cover installedaround the frame.
 4. A method for making a backrest comprising thefollowing steps: providing a frame including a margin and two rimsextending on a side of the margin and a gap defined between the rims;providing a web; providing a ring; providing a mold assembly including:a lower mold defining a cavity in an upper side; a middle mold; and anupper mold defining a cavity in a lower side; putting the frame in thecavity of the lower mold with the rims facing up; holding the frame inposition by means of lowering the middle mold against the margin, withthe rims exposed. spreading the web on the middle mold, with the webcovering the rims; forcing the ring and an annular portion of the webinto the annular groove so as to tightly spread the web on the frame;pressing the ring, the web and the frame against one another by means oflowering the upper mold against the ring; and adhering the frame, theweb and the ring to one another; returning the upper mold and the lowermold to their original positions; and removing the frame, the web andthe ring, as a whole, from the middle mold.
 5. The method according toclaim 4 wherein the step of adhering the frame, the web and the heatpressing the ring to one another includes a step of partly melting them.6. The method according to claim 5 wherein the step of partly meltingthe frame, the web and the ring includes a step of heating them.
 7. Themethod according to claim 6 wherein the step of heating the frame, theweb and the ring includes a step of exerting high frequency on them. 8.The method according to claim 4 including a step of providing a cushionbetween the margin and the web so that the web is more tightly spread onthe frame.
 9. The method according to claim 4 including a step ofproviding a cover around the frame.